124 CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIPTERA HETEROPTERA. 



Second Maturation Division. — A pole view of a daughter chromosomal plate of 

 the first nuituration mitosis (Plate XII, Fig. 196) shows 9 elements; the 2 central 

 rounded ones are the univalent diplosomes, and outside of them is a circle of 7 univa- 

 lent diplosomes the constriction of each being its longitudinal split. As these come 

 to ai'range themselves in the equator of the second spindle there appear to be only 8 

 instead of 9 of them ; this is because the univalent diplosomes have conjugated in the 

 centre to form a bivalent one (Fig. 197). This bivalent element can be recognized 

 only by its central position because its components are of equal volume (/>/, di, Fig. 

 198). Each of the 7 autosomes divides equationally, but the bivalent diplosome 

 divides reductionally. And each spermatid exhibits always exactly 8 elements of 

 which the central one is a diplosome (Fig. 199). 



27. Pkliopelta akbreviata Uhler. 



Spermatogoni-c Division. — There were on my preparations only two fairly clear 

 pole views of the equatorial plate (Plate XII, Figs. 200, 201), and in each of these the 

 elements were more or less obliquely placed. There are in all 14 chromosomes, 10 of 

 which are noticeably larger and 4 considerably smaller. The following history shows 

 that these 4 smaller ones are diplosomes, which compose a larger pair {Di. 2, di. 3) and 

 a smaller pair [Di. 1, di. 1). 



Gro'wth Period. — From the synapsis stage (Fig. 202) there are in each nucleus, 

 besides the long loops of the Ijivalent autosomes, 2 large dense bodies of equal volume ; 

 and when the autosomes become longitudinally split each of these becomes constricted 

 at its middle point [Di. 3, di. 3, Fig. 203). By their size relations these are evidently 

 the same as the pair of larger diplosomes of the spermatogonia, for they are much too 

 large to correspond to the smaller pair. They may be apposed (Fig. 202) or may be 

 separated (Fig. 203). The smaller diplosomes could not be distinguished with cer- 

 tainty at this time, whence it is likely that they undergo changes like the autosomes do, 

 or at least do not remain dense and safraninophilous. The 10 large autosomes Join 

 end to end to form bivalent elements, and each becomes longitudinally sjjlit ; they 

 are then mostly in the form of a U or a V and the split in the arm of each remains 

 narrow and never opens up widely. 



First Maturation Division. — In the prophases condense 5 large tetrads, which are 

 the bivalent autosomes; a single one of them is drawn in Fig. 204, and 4 in Fig. 205, 

 they being the bodies that are not lettered ; these may condense so as to appear nearly 

 solid and very massive, but frequently the point of J unction of the univalent elements 

 continues recognizable as well as the longitudinal split in each of the latter, and this 

 split is always parallel to the long axis. Next in size to these are 2 elements 



